Three-spring soil reaction model for wind turbine monopile foundation in clay

Abstract

Precisely estimating the lateral capacity of the large-diameter monopile is essential for securing the stability of the fixed wind turbine of high power generation. Conventional standards relying on p-y curves often underestimate the monopile-soil interaction due to their failure to account for pile shaft rotations and base effects, leading to overly cautious lateral capacity designs. This paper introduces the three-spring soil reaction model that comprehensively considers lateral soil resistance, shaft frictional resistance, base shear force, and base moment. The analytical expressions for three springs are established considering the self-similarity between soil stress-strain relationships and load-displacement responses. The bearing capacity calculation method of monopiles with varying rigidity is developed based on the combinations of three springs. The results reveal that the modified p-y curve for lateral capacity predictions achieves over 80% accuracy. The contributions of base effects and shaft frictional resistance to bearing capacity gradually increase with the increases in pile rigidity, and the correction of monopile ultimate lateral displacement prediction is also enhanced.